The present invention relates to a safety or seat belt retractor, and more particularly, to an improved dampening mechanism that more reliably prevents loose windings cf the safety or seat belt from forming during take-up, while providing full winding speed during an initial take-up period.
Various safety belt retraction arrangements have been suggested to take up and pay out safety belts, i.e., seat belts and shoulder straps, about a vehicle occupant. In some of the automatic or so called passive seat belt systems, the seat belt retractor is mounted on the vehicle door and swings with the door, experiencing rapid accelerations and decelerations as the door is thrown open or is slammed shut. In swinging the door shut from the fully opened position, the seat belt retractor retracts the seat belt quickly to prevent the seat belt webbing from being caught between the door and the door molding. That is, if the seat belt webbing is not being wound quickly it will form a loop at the space between the door and the door molding and the loop will be caught therebetween before the retractor can wind the loop material or to the reel. With substantial rewind springs in these door mounted retractors, the retractors have been able to rewind the seat belt sufficiently fast that no loop is formed and caught between the door and the vehicle door molding. In some instances, another problem arises with this very fast winding of the seat belt in that slamming of the vehicle door results in a shifting of the retractor locking bar or pawl into a locking position, which prevents paying out of the seat belt, thereby effectively preventing the operator from gaining access to the interior of the vehicle. It appears that because the coils of seat belt are being wound so fast on the reel when the door is being slammed shut with high acceleration, that the coils of the seat belt are loose rather than tight and that when the door hits the soft resilient molding it compresses the molding as it abruptly decelerates. In some instances, the deceleration is sufficiently fast that the inertia weight is operated to move the lock bar into locking position and as the door rebounds and the "over-compressed"molding expands to a steady state configuration, the seat belt is pulled outwardly, taking up the slack from the loose coils and ratchet teeth on the ratchet engage the lock bar and hold the lock bar in its locking position because of the rake on the ratchet teeth. If someone subsequently tries to open the vehicle, he can not gain entry because the seat belt retractor is locked against any paying out of the seat belt, including pay out necessary to open the door. Of course, such sequence of actions to inadvertently lock the door are rare but are desired to be avoided.
One attempt at an inexpensive solution for eliminating loose windings of a safety belt during take-up has been proposed for retraction mechanisms mounted inside of a housing made of polypropylene or other plastic material. In arrangements of this type, a snorkel on the housing has a belt guiding slot for passage of a safety belt therethrough. In the proposed solution, the slot size is decreased to the point where the side walls forming the slot frictionally engage the safety belt and retard the movement of the belt at high speed travel. One problem in hot climates is that the temperature of the plastic housing may be raised to the point where it softens to the extent that the frictional grip is substantially reduced. Also, the continued rubbing of the belt on the plastic will wear the same and increase the slot opening at some point in the life of the vehicle.
It is therefore desirable to provide a retraction apparatus which is fast-acting during initial take-up, and which tensions or dampens the safety belt only during later stages of take-up. Several such arrangements have been shown. For example, U.S. Pat. No. 4,262,922 issued Apr. 21, 1981, to Fox discloses a dampening device for a seat belt retractor, having a friction wheel disposed in a hollow gear. The dampening prevents loose winding of the seat belt webbing during take-up within the retraction device. A plunger actuated by a vehicle door applies a locking force to the hollow gear, through a cable arrangement. Once locked, the hollow gear applies a friction force to the friction wheel through a wave spring. The arrangement, although capable of providing dampening after a certain amount of take-up has occurred, is costly to fabricate and install in a vehicle, and has a number of moving parts that can fail or otherwise create other operating difficulties.
U.S. Pat. No. 4,378,916 issued Apr. 5, 1983,to Keinberger discloses a safety belt wind-up device having a rubber-coated roller mounted for movement toward a webbing reel. The safety belt webbing is wrapped over the roller, and when tensioned, pulls the roller into contact with webbing previously wound on the reel. This provides frictional engagement with the webbing to prevent payout, and reduces spooling --that is, extra peyote after the retractor has been locked, which tightens loose windings. While providing a primary locking of the webbing reel, this arrangement fails to provide a dampening that reduces or eliminates loose windings of webbing about the take-up reel, and does not provide a dampening that occurs only after a predetermined amount of take-up is accomplished.
U.S. Pat. No. 4,381,085 issued Apr. 26, 1983, to Stephenson et al. is similar to Keinberger, but replaces the rolling friction wheel with a reciprocating block-like clamp. Operation is the same as in Keinberger, and suffers from the same deficiencies in that it fails to disclose a tensioning arrangement which eliminates loose winding of the webbing about a take-up reel, and does not provide a selective tensioning that occurs only after a predetermined amount of take-up is accomplished.
U.S. Pat. No. 4,153,996 issued May 15, 1979, to Rutty discloses a combination blade lock and shock absorber for a coilable rule comprising a lever which is mounted for both pivoting and translational movement. The blade of the rule passes between the lever and a rule housing. Brake shoes formed in the lever engage the blade as the lever is pivoted by a bias spring. The lever, under the action of the spring, presses the blade against the rule housing to provide a brake action which can be overcome by an operator on pivoting in an opposite direction. The free end of the blade has a dependent hook which, upon blade retraction into the housing, contacts the lever, causing a translational displacement thereof which works against the same bias spring mentioned earlier. This latter action provides a shock absorber when the blade is retracted into the housing. While providing a braking mechanism, this patent fails to disclose an arrangement for tensioning or dampening the web during take-up, let alone a selective dampening that occurs only after a predetermined amount of take-up is accomplished.